1. Field of Invention
The present invention relates to a shock absorber, in particular to an automatic shock absorber for a rotating device.
2. Description of Related Arts
The primary factor leading to the vibration is the mass unbalance of a rotating system. On-line automatic balance is the best scheme for improving the balance level of the rotating system and reducing the vibration.
At present, an automatic balance actuator of rotating machinery mainly involves two kinds of products: an electromagnetically mechanical balance actuator and a liquid injection-balance actuator.
The liquid injection-balance actuator has a simple structure. However, the actuator has less balance capability as the number of the balance increased, without shutdown hold function, so that liquid is required to be injected into the chamber rotating at high speed, and there is more uncertainty in terms of injection volume and the splash also has a certain influence on the surroundings. Because there is difficult to isolate the injection process from the surroundings, dust and other foreign matter are easy to be brought in and there is resistance change in the injection hole with small aperture, resulting in the decreased system control performance and even out of control.
The U.S. Pat. No. 4,537,177, which is titled “BALANCED ROTARY SAW ASSEMBLY AND A METHOD OF BALANCING THE SAME” and filed in 1985, disclosed an injection balancing device moved by driving the balancing liquid with compressed gas. In this patent, two opposite chambers were connected with two communicating tubes and a check valve with a movable element was also installed in the communicating tube, thus the balancing liquid in each communicating tube only could flow in one direction. The device was complex and the increase of the applicable speed was restricted by the movable element rotating with the device, therefore, the device only can be used for the on-line automatic balancer of a slowly rotating device such as a saw and the like. Furthermore, a minimal unbalance can create extremely high unbalanced centrifugal force in a high-speed rotating device, resulting in the severely vibration of the device.